Generally, 3D printing involves the use of an inkjet type printhead to deliver a liquid or colloidal binder material to layers of a powdered build material. The printing technique involves applying a layer of a powdered build material to a surface typically using a roller. After the build material is applied to the surface, the printhead delivers the liquid binder to predetermined areas of the layer of material. The binder infiltrates the material and reacts with the powder, causing the layer to solidify in the printed areas by, for example, activating an adhesive in the powder. The binder also penetrates into the underlying layers, producing interlayer bonding. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final object is formed. See, for example, U.S. Pat. Nos. 6,375,874 and 6,416,850, the disclosures of which are hereby incorporated herein by reference in their entireties.
Apparatus for carrying out 3D printing typically generate dust, which can detrimentally effect the operation of the printheads. For example, the dust can clog the jet nozzles that dispense the binder material, which can result in no binder material being dispensed or the binder material being dispensed inaccurately.
Powder handling and powder and dust management are major problems in 3D printing. Loading powder into the feed piston generally involves lifting a heavy bucket of powder and pouring it in. This always causes a large dust cloud and often results in a lot of powder being spilled. The printing process also stirs up a lot of dust by spreading powder and dumping it into an overflow container. Once the part is printed, the unprinted powder must be removed from the build box in a process that is tedious and often very messy. The overflow container must be emptied back into the feed piston and this also involves lifting a heavy container, pouring powder out of the container, and the generation of a dust cloud, and often, spilled powder. Depowdering the part after it has been printed creates additional problems. Because of cost, most users want to recycle the powder removed from the part. Currently, this involves removing a vacuum bag from a vacuum cleaner, tearing it open, and pouring the powder into the feed piston. A sifting step is usually required, because broken pieces of a printed part may be vacuumed up. Both of these processes are extremely messy and get powder on the user, the floor, and the machine, and create dust clouds.
It is, therefore, an object of the present invention to provide apparatus and methods for automatically handling powder throughout a 3D printer system to reduce waste and minimize contamination of the system and surrounding area from loose powder.